IMPORTANT:
--enable-dio is NOT recognized as an option. After reporting a bug, i got following answer:
It is not bundled anymore. See http://pecl.php.net/dio to fetch the CVS version (being unmaintained, there is no release in pecl). Not a bug > bogus.to use mandatory locking on a linux system, the filesystem has to be well prepared.
# /etc/fstab: static file system information.
#
# <file system> <mount point> <type> <options> <dump> <pass>
/dev/hda1 / ext3 errors=remount-ro,mand 0 1
/dev/hda2 none swap sw 0 0
proc /proc proc defaults 0 0
/dev/fd0 /floppy auto user,noauto 0 0
/dev/cdrom /cdrom iso9660 ro,user,noauto 0 0
For example here the ext3 partition has been prepared for mandatory locking. Otherwise no dio_function will work on the system.